10.1
Upper Air Temperature Variations and Change
John R. Christy, Univ. of Alabama, Huntsville, AL
Variations in the vertical temperature structure of the atmosphere have implications for detection and attribution issues regarding global climate change. Several data sources for upper air temperatures are examined and provide a fairly consistent picture since 1958 of tropospheric warming (approx. +0.10 K/decade) and stratospheric cooling (approx. -0.30 K/decade). The period since 1979 is examined more closely and indicates global tropospheric warming has been slight (approx. +0.05 K/decade). The various troposheric datasets (satellite-based, radiosonde-based and reanalyses) are divided into latitudinal sections and all are consistent in showing strongly positive trends in the 20N-90N band, with zero or slightly negative trends over the remainder of the globe in the past 20 years. Significant cooling of the lower-stratosphere has been observed (approx. -0.6 K/decade). And, since 1979, middle and upper stratospheric cooling is substantial. Explanations for these patterns of change include variations in responses to ENSOs, volcanic events, ozone depletion, increases in greenhouse gasses, as well as variations due to fluctuations in modes of atmospheric circulation such as the North Atlantic and Arctic Oscillations.
Session 10, IPCC TAR: Long-term Climate Variability and Change: Part 3 (Parallel with Joint Session J1)
Wednesday, 12 January 2000, 3:30 PM-5:30 PM
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